Multi-Section Crystal Bandstop Filter Design

This article describes two extensions of the Holt-and-Gray technique, which yields multi-section narrowband crystal bandpass filters with elliptic filter characteristics in both passbands and stopbands. The first extension is relatively minor, in that it refers to a computer patch which is used to minimize the spread of crystal motional parameters throughout the various sections. As described it is interactive, but could be made the objective function of an optimization routine if desired.